UAVs are already playing a major role in most conflict zones in the world. Current conflicts are between the 'haves and the have-nots', but surely this will not always be the case. UAV's will be incredibly hot export items in the arms trade, and probably in the drug trade as well at some point.
The implications for air defense will get real complicated real quick: Is there an IFF protocol for 'our' UAV's? What systems are being designed to deal with small recon or arty spotting/designating UAV's?
Spotting and then hitting a small craft with a 5' wingspan from 1500 meters is beyond any of the US' current ground-based capabilities at this point, is it not? Larger UAVs the size of a Predator may be vulnerable to air-to-air engagements, but what else do we have to shoot at them from the ground but for Patriot or Stinger missiles? Neither is really suited for the job - could a Stinger even 'see' the IR signature of a Predator at 5000 meters?
The Germans have the excellent Gepard (and the Chinese have a similar system). Whadda we got? the Linebacker with the 25mm popgun that has no credible AAA round? Time to think AHEAD, as in 35mm AHEAD.